This invention is concerned with sewing machines; more particularly, with a needle looper assembly for lockstitching with a non-threaded needle.
Until somewhat recently, lockstitch sewing machines utilized an upper needle having a thread carrying eye located at the tip thereof to carry a loop of upper thread downwardly through a work material to a loop taker for pick up thereby and concatenation about a lower thread. However, a system was disclosed in U.S. Pat. No. 4,245,577 issued on Jan. 20, 1981, application Ser. No. 033,297, filed on Apr. 25, 1979, which utilized a needle looper extending upwardly through a work material to receive a loop of upper thread and draw this upper thread down to a looptaker. The upper thread was then taken by the looptaker and passed about a lower thread supply to concatenate the upper thread with the lower thread so as to form a lockstitch. In this prior art device, a needle looper assembly was used which was vertically reciprocated by a crank arrangement, and utilized a special cam to generate relative movement between an outer needle and an inner rod which carried a hook on the extremity thereof. This orientation of the needle looper assembly is rather cumbersome in that it greatly enlarges the depth of the sewing machine bed.
What is required is a simplified arrangement of a needle looper assembly which requires substantially less vertical room so as to be compatible with the accepted envelope for a sewing machine frame. It would be further desirable to simplify actuation of the arrangement for capturing the upper needle thread, as well as the arrangement for sweeping the upper thread into the needle looper.